Ink-jet printers are well known in the art, and many utilize a carriage which carries one or more ink-jet cartridges or pens in a traversing or scanning movement transverse to the printer paper path. It is also known to provide an external stationary ink reservoir connected to the scanning cartridge via a tube. The external reservoir is typically known as an "off-axis" ink reservoir. While providing increased ink capacity, these off-axis systems present a number of problems, however. The space requirements for the off-axis reservoirs and tubing impact the size of the printer, with consequent cost increase. Moreover, pressure drops through the tubing can reduce printer throughput and affect printing quality. Another problem is that of vapor losses from the tubing and air diffusion into the tubing system. In the past, tubing such as LDPE (low density polyethylene) has been used, since it is a low modulus material which is easy to bend. This low modulus material suffers from relatively high vapor losses and air diffusion into the tube. As a result of the vapor losses, the ink can change properties, degrading print quality and eventually causing tube or printhead clogging. As a result of air ingestion, the printhead can fill with air. During thermal fluctuations, the air can expand, causing printhead drool. In addition, the air can cause printhead starvation. Further problems include the force exerted on the carriage by the tubing, and the stresses on the tubing that tends to cause buckling or fatigue failures. These problems are exacerbated with a low end off-axis printing system with its relatively small form factor.
It would therefore be an advantage to provide a compact, low end off-axis printing system.
It would further be advantageous to provide such a printing system which permits high throughput printing, with relatively high flow rates through the tubing.
Still other advantages would be provided by an off-axis printing system with high reliability due to low vapor losses and air diffusion, yet with minimal tubing pressure drops while minimizing the force exerted by the tubing on the carriage to maintain accurate printhead alignment.